1. Field of the Invention
The present invention relates to a recording apparatus for an optical recording medium.
2. Description of the Related Art
At present, an optical recording medium having a recording capacity of several gigabytes is in practical use such as a DVD-R (Digital Versatile Disc-Recordable). Development is pursued for a higher performance optical medium such as a rewritable DVD-RW (DVD-Re-recordable). The remarkable improvement of the performance of the mass storage digital optical recording medium and the reproducing apparatus has made it possible to record a large amount of data with a high quality.
On an optical disc as described above, there are formed a groove track serving as a recording track for information data, and a land track as a guide track for guiding a laser beam as a reproducing light beam or a recording light beam to the groove track. A land prepit (also simply referred to as a prepit) corresponding to pre-information (pre-recording information) is formed on the land track. The prepit bears the pre-information, which is used by an information recording and reproducing apparatus during recording and/or reproduction of data, namely, address and synchronization information used to recognize a location on the groove track. The prepit is formed beforehand prior to the shipment of the optical disc.
The groove track is wobbled at a frequency corresponding to the rotational speed of a disc. Like the prepit, the wobbled groove track is formed beforehand prior to the shipment of the optical disc.
When information data to be recorded (hereinafter simply referred to as information data or data) is recorded on the optical disc, the information recording apparatus extracts the wobble frequency of the groove track, thereby controlling the optical disc at a predetermined rotational speed. The information recording apparatus also detects the prepit, thereby acquiring the prepit information. Address information indicating a location on the optical disc is thus obtained. Based on the address information, the information data is recorded on a recording position.
A light beam is directed to the optical disc with the axis of the light beam aligned with the center of the groove track during the recording of the information data. Information pits are thus formed on the groove track in accordance with the information data. The information data is thus recorded. The light beam partly irradiates the land track, and a portion of light is reflected from the land track. The pre-information is acquired in the reflected light beam from the prepit using, for example, a push-pull method. A wobble signal is extracted from the beam reflected from the groove track, and a recording clock signal in synchronization with the rotation of the disc is thus obtained. The information data recorded on the optical disc is split every sync frame (hereinafter simply referred to as a frame) with each split data becoming a unit of information. Each sync frame contains synchronization information at the head end position thereof to maintain synchronization every sync frame.
There is a possibility that the information data (e.g., the synchronization information and the address information) is deviated in position from the originally intended synchronization position thereof with respect to the position of the prepit because of external disturbances when the information data is recorded. For example, when the information data is recorded to a point that goes far beyond the originally intended synchronization position, the data is recorded based on the position information of the prepit, thereby partially overwriting previously recorded data. If an overwriting recording occurs, the DVD-R disc is subject to an error in which both previously recorded data (old data) and currently recorded data (new data) cannot be read. In a case of the DVD-RW disc, new data can be read while the old data is destroyed.
Furthermore, a deviation of the recording position causes an unrecorded portion between the recording position of the old data (the tail or end position thereof) and the recording position of the new data (the head position thereof). If such an unrecorded portion occurs, no correct servo signal is obtained from a reproducing apparatus, and a tracing failure could take place. If an overwritten portion or an unrecorded portion takes place, no consistency is maintained between sync information position intervals, and data could be recognized as a faulty block during reproduction.